The present invention relates to digital media storage. Specifically, the invention relates to apparatus, methods, and systems for increasing recording throughput on digital media recording systems.
Magnetic recording has played an important role in the electronic age for permanently storing and retrieving data. Magnetic recording media such as magnetic tape cartridges provide compact, reliable storage at a relatively low cost. In addition to storing data processing files, magnetic media have also been widely used to store data related to digital convergence such as digital music, video, photos, and personal data. Consumers and businesses have clearly benefited from the versatility of this constantly improving, media.
Despite the ubiquitous usage of magnetic storage, other types of storage such as flash memories have increased in popularity relative to magnetic storage. Part of the appeal of non-magnetic storage relates to the increased storage bandwidth or throughput available with such technologies albeit at a significantly higher cost per Megabyte of storage. What is needed are means and methods to improve the storage bandwidth of magnetic media systems.
One bottleneck on magnetic recording systems involves data compressionxe2x80x94particularly context-based data compression of text and binary data files. FIG. 1 illustrates a block diagram of a typical prior art storage unit 100. The storage unit 100 includes a host interface 110, a compression module 120, a media interface 130, a recording medium 140, and a controller 150. The storage unit 100 illustrates some of the challenges related to increasing data compression bandwidth within digital media recording systems in general and of magnetic recording systems in particular.
The host interface 110 receives data 102 and commands 104 from a host or other computer-based system. Typically, the host interface directs the commands 104 to a control bus 106, and the data 102 to high-speed data bus 108, or the like. The controller 150 may receive the commands on the control bus 106 and direct operations related to recording data to or retrieving data from the recording medium 140.
The recording medium 140 is typically limited to a certain recording and retrieval rate for each track recorded on the recording medium 140. However, data throughput may be increased by recording and retrieving multiple tracks concurrently. As a result, many recording systems have increased the number of concurrently written tracks, the bandwidth of the media interface 130, and the aggregate data transfer rates associated therewith.
The compression module 120 compresses data and thereby potentially increases the effective throughput seen by the host to, and the capacity of, the storage unit 100 in that more information may be stored with less data written to media. However, the data transfer rates of the compression module 120 may be limited by semiconductor clock rates in that many compression algorithms, particularly context-based compression algorithms such as SLDC, compress on a byte boundary and thus are not readily extensible to compress more than one byte at a time. This is particularly problematic for data processing systems that rely heavily on context-based compression to compress text files, binary data files, and the like.
The limits of context-based compression algorithms place system designers in a quandary. On one hand, compression potentially increases the throughput and storage capacity of digital recording media such as magnetic media. On the other hand, compression places an upper bound on data transfer rates achievable with context-based compression.
What is needed are apparatus, means, and methods to increase the throughput achievable with digital recording media. In particular, what is needed are apparatus, methods, and systems to overcome the bottleneck currently associated with context-based compression within digital media recording systems.
The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available digital recording means and methods. Accordingly, the present invention has been developed to provide an apparatus, method, and system to overcome many or all of the above-discussed shortcomings in the art.
In one aspect of the invention, an apparatus for increased recording throughput of digital media recorders includes a control module that distributes a source data stream to multiple compression paths that compress and buffer digital data to provide compressed data streams, and one or more media encoders that concurrently encode the compressed data streams to corresponding media tracks. In one embodiment, the control module monitors available buffer space within each compression path and distributes data to a selected compression path based on available buffer space. Each compression path may include a compression module that provides compressed data and a data buffer that buffers the compressed data.
In addition to distributing data to a selected compression path, the control module may initiate insertion of metadata within the compressed data streams that facilitate reconstruction of the source data stream from the corresponding set of compressed data streams. In certain embodiments, the metadata includes a swap command indicating selection of a particular compression path. The control unit may also adjust distribution of the source data stream based on feedback from a media encoder, such as skip events due to media defects on particular tracks, which slow or pause the throughput of one of the compression paths to media. The source data stream may be distributed in units large enough to maintain context and compressibility of the data.
In one embodiment, the media encoder encodes an active path identifier at each access point within the media tracks and each access point corresponds to a point in the compressed data stream that is context-free. The active path identifier identifies the active or xe2x80x98hotxe2x80x99 path from which the compressed data is preferably directed from for decompression. Placing an active path identifier at each access point facilitates decompressing data and reconstructing the original source data stream beginning at any access point.
In another aspect of the invention, an apparatus for increased retrieval throughput of digital media recorders includes one or more media decoders that concurrently decode multiple media tracks to provide a set of compressed data streams to a corresponding set of decompression paths that concurrently decompress and buffer the compressed data streams to provide a corresponding set of decompressed data streams, and a control module that merges the decompressed data streams into a merged data stream as directed by metadata contained within the compressed data streams. Each decompression path may include a decompression module that provides decompressed data and a data buffer that buffers the decompressed data.
In certain embodiments, the metadata comprises a swap command indicating selection of a particular decompression path. In one embodiment, the media decoder decodes an active or xe2x80x98hotxe2x80x99 path identifier at each access point within the media tracks in order to commence decompression beginning at any access point. In certain embodiments, the described functional units of the data recording and data retrieval units are merged into a single unit that streams data to and from a digital medium on parallel tracks in an efficient concurrent manner.
In one aspect of the invention, a method for increased recording throughput on digital media recorders includes distributing a source data stream to multiple compression paths to concurrently provide a corresponding set of compressed data streams, inserting metadata within the compressed data streams, and concurrently encoding the compressed data streams to media tracks. The metadata facilitates reconstruction of the source data stream from the compressed data streams. In certain embodiments, the method also includes monitoring available buffer space within each compression path, and distributing the compressed source data stream to a given path based on available buffer space within each compression path.
In one aspect of the invention, a method for increased retrieval throughput of digital media recorders includes concurrently decoding media tracks to provide corresponding compressed data streams, concurrently decompressing compressed data streams to provide decompressed data streams, and merging the decompressed data streams into a merged data stream as directed by metadata contained within the compressed data streams.
The present invention increases throughput of digital media recording systems by intelligently distributing a source data stream to multiple compression paths and inserting metadata within the resulting compressed data streams that facilitate reconstruction of the source data stream. The present invention adjusts to media defects and variations in data compressibility in a transparent manner. These and other features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.